High temperature ceramic oxide superconductor compounds known in the art include materials in such systems as Y-Ba-Cu-O, Tl-Ba-Ca-Cu-O, La(Sr, Ba)-Cu-O, Bi-Sr-Ca-Cu-O, as well as related materials.
Several high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductors are known. For example, Tarascon et al. in "Crystal Substructure and Physical Properties of the Superconducting Phase Bi.sub.4 (Sr, Ca).sub.6 Cu.sub.4 O.sub.16+x ", Phys. Rev. B., 37, (16), 1988, pp. 9382-89, describe the crystal structure and superconductive properties of Bi.sub.4 (Sr, Ca).sub.6 Cu.sub.4 O.sub.16+x and Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.8.13.
Thin films of high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductors have been deposited onto planar substrates by several techniques. For example, Laibowitz in "High T.sub.c Superconducting Thin Films", M.R.S. Bull., Jan., 1989, pp. 58-62, discusses the deposition of high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductors onto wafer-shaped substrates such as Al.sub.2 O.sub.3, MgO, SrTiO.sub.3, Si, LaGaO.sub.3, and ZrO.sub.2 stabilized with Y.
Methods known in the art for depositing thin films of high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductors include a variety of conventional vacuum techniques, such as magnetron sputtering, laser evaporation, and co-evaporation. (See e.g., "Processing Science and the Technology of High T.sub.c Films", Bunshah et al., Res. and Dev., Jan., 1989, pp. 65-79.)
Several solution-based techniques for depositing high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductors onto substrates such as ZrO.sub.2, MgO, and SrTiO.sub.3, are also known in the art. For example, Cooper et al. in "Bismuth Strontium Calcium Copper Oxide High-T.sub.c Superconducting Films From Nitrate Precursors," Mat. Lett., 7, (1,2), 1988, pp. 5-8, teach a superconducting film of bismuth strontium calcium cuprate prepared by spray pyrolysis of aqueous nitrate solutions onto heated (100) oriented MgO, yttria-stabilized zirconia, and SrTiO.sub.3 substrates. Although spray pyrolysis allows greater flexibility in the choice of precursor chemistry than other known solution-based techniques, the process requires spraying a precusor solution onto a heated substrate (typically heated to a temperature in the range of 400.degree. to 600.degree. C.), atomization of the precursor solution, and careful control of the impingement velocity of the atomized precursor solution.
Furcone et al. in "Spin-on Bi.sub.4 Sr.sub.3 Ca.sub.3 Cu.sub.4 O.sub.16+x Superconducting Thin Films From Citrate Precursors," Appl. Phys. Lett., 52, (25), 1988, pp. 2180-82, describe the synthesis of thin films in the Bi-Sr-Ca-Cu-O system from homgeneous liquid citrate precursors coated on to single-crystal SrTiO.sub.3, Y-stabilized cubic ZrO.sub.2, and (100) oriented MgO substrates by spin-coating and heat-treatment methods. The authors noted, however, that the viscosity of their precursor solution, which was highly variable, was dependent on the thermal history and the specific yield of the solution.
Nasu et al. in "Preparation of BiSrCaCu.sub.2 O.sub.x Films with T.sub.c &gt;77 K by Pyrolysis of Organic Acid Salts," Jap. J. Appl. Physics, 27, (4), 1988, pp. L536-37, disclose the preparation of a high temperature superconducting BiSrCaCu.sub.2 O.sub.x film on yttria-stabilized zirconia substrates using bismuth, strontium, calcium, and copper 2-ethylhexanoate precursors.
EPO Patent Application No. 0 287 258 describes a method for forming a cuprate-based high temperature ceramic oxide superconductive layer on a substrate, such as MgO, ZrO.sub.2, SrTiO.sub.3, Au, or Ag, by applying a precursor solution onto a major surface of the substrate, (e.g., by spraying, dipping, spin-casting), heating the coated substrate to a temperature in the range of 400.degree. to 450.degree. C., heating the substrate in an oxygen atmosphere to a temperature in the range of 820.degree. to 1000.degree. C. such that the perovskite phase associated with superconductivity in YBa.sub.2 Cu.sub.3 O.sub.7 is formed, and then oxygenating the perovskite phase in an oxygen atmosphere at a temperature in the range of 300.degree. to 500.degree. C. The preferred cuprate-high temperature ceramic oxides disclosed were represented by the generalized formulas,
Ba.sub.2-x M.sub.1-y X.sub.x+y Cu.sub.3 O.sub.9-.delta.,
wherein M is one of Y, Eu, or La; X is none or one or more of Ba, Y, Eu, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Ca, and Sr; O.ltoreq.x+y.ltoreq.1; and 1.5&lt;.delta.&lt;2.5; and
La.sub.2-x M.sub.x CuO.sub.4-.epsilon.,
wherein M is one or more divalent metals such as Ba, Sr, and La; x.gtoreq.0.05; and O.ltoreq..epsilon..ltoreq.0.5. The authors, however, do not teach a method for depositing a high temperature Bi-Sr-Ca-Cu-O-based ceramic oxide superconductive phase onto a substrate.